This invention relates to a method and apparatus for a thin film resistor having a tantalum pentoxide moisture barrier.
Current film resistors and the associated processes of making such resistors have had problems with the ability to create or use an effective moisture barrier. A moisture barrier is that layer that is deposited on the surface of the resistor in order to prevent moisture in the form of condensation or vapor from degrading the resistive film element. Screen-printed material has been used as a moisture barrier and this has been shown to reduce the failure rate of the resistor due to moisture. However, problems remain.
Tantalum pentoxide has been used in the semiconductor industry as an insulator and to improve recording performance of cobalt alloy media on glass-ceramic disks. Tantalum pentoxide has been used within the resistor industry to improve resistive elements integrated with spark plugs and to form a graze resistor. It is also associated with a tantalum nitride resistive system that prevents moisture failure. It is recognized that tantalum nitride resistors have a naturally occurring layer of tantalum pentoxide, the result of an oxidation process. Further, tantalum nitride resistors and tantalum nitride capacitors are known for their resistance to moisture.
Many thin film resistors, especially those of nickel-chromium alloys and other alloys containing nickel, chromium, and other metals are particularly susceptible to moisture conditions. These and other types of alloys have a failure mode of electrolytic corrosion that is capable of causing an electrical open under certain moisture conditions. In particular, under powered moisture conditions, electrolytic corrosion can occur and the resistor can fail. This makes the thin film resistor unsuitable for applications where moisture conditions may occur.
Thus, it is a primary object of the present invention to provide an improved method and apparatus for a moisture barrier for film resistors.
Another object of the present invention is to provide a method and apparatus for a film resistor which is less susceptible to powered moisture testing.
Another object of the present invention is to provide a method and apparatus for a moisture barrier capable of use with nickel-chromium, alloy thin film resistors.
Yet another object of the present invention is to provide a method and apparatus for a moisture barrier for thin film resistors that does not require tantalum nitride.
Another object of the present invention is to provide a method and apparatus for a moisture barrier for a thin film resistor replaces screen-printed moisture barriers.
Yet another object of the present invention is to provide a method and apparatus for a moisture barrier for a thin film resistor that is compatible with normal manufacturing techniques and materials.
A further object of the present invention is to provide a method and apparatus for a moisture barrier for a thin film resistor that can be used with nickel and chromium alloys.
Yet another object of the present invention is to provide a method and apparatus for a moisture barrier for a thin film resistor that performs favorably under MIL-STD-202method 103 testing.
A further object of the present invention is to provide a method and apparatus for a moisture barrier for a thin film resistor that performs favorably under MIL-STD-202 method 106 testing.
Yet another object of the present invention is to a method and apparatus to reduce or eliminate failures of thin film resistors due to electrolytic corrosion under powered moisture conditions.
Another object of the present invention is to provide a method and apparatus for a moisture barrier that may be deposited through sputtering.
These and other objects, features, or advantages of the present invention will become apparent from the specification and claims.